In Table REF , we report the performance of PolarMask [1]} on our dataset. As is shown in the table, PolarMask can not solve the instance segmentation of irregular objects. That is because PolarMask can only represent a thirty-six-side mask due to its limited number of rays. Hence, it can not handle objects with hollow, for example, the fences. Also, they distinguish different instances according to center regression, which, however, can not handle instances that share the same center. We also find that PolarMask can only tackle some cases of logs in iShape, which looks like circles on the side and fit its convex hull mask setting.
